1. Field of the Disclosure
This disclosure relates to a liquid crystal display (LCD) device, and more particularly to an LCD device which can reduce manufacturing costs by forming a separate conductive pattern on a balance printed circuit board (PCB) to enable driving of a scanning backlight.
2. Description of the Related Art
In general, a liquid crystal display (LCD) device uses an optical anisotropic characteristic and a polarization characteristic of a liquid crystal material as a principle component in forming an image. Liquid crystal has a thin and lengthy molecular structure and exhibits the anisotropic characteristic of having directivity in an array and the polarization characteristic of the direction of a molecule array varying according to the size thereof when placed in an electric filed. A liquid crystal panel is an essential constituent element, including a pair of transparent insulation substrates. An electric field generation electrode is formed on each of surfaces of the transparent insulation substrates that face each other with respect to a liquid crystal layer interposed between the substrates. The arrangement direction of liquid crystal molecules is intentionally adjusted by a change in the electric field between the electric field generation electrodes. Accordingly, transmissivity of light is varied so that a variety of images can be displayed.
Since the liquid crystal panel is a device without a self-illuminating element and requires a separate light source, light is supplied by a backlight unit provided at a rear surface to form an image of a sufficient brightness to view. According to the arrangement method of an illumination lamp included in the backlight unit, the backlight unit may be classified into an edge type and a direct type. In the edge type backlight unit, an illumination lamp is arranged at an edge of one side of a rear surface of a liquid crystal panel and light of the illumination lamp is refracted by a light guide plate to be incident on the entire surface of the liquid crystal panel. In the direct type backlight unit, a plurality of illumination lamps are arranged on a rear surface of the liquid crystal panel and light of the illumination lamps is directly supplied over the entire surface of the liquid crystal panel.
The edge type backlight unit can be easily manufactured because a tube-like illumination lamp is installed at the side surface of the liquid crystal panel and light of the illumination lamp is supplied to the overall surface of the liquid crystal panel using a transparent light guide plate. In contrast, the direct type backlight unit does not need a light guide plate because light is emitted directly to the overall surface of a substrate and exhibits a high light use efficiency because a plurality of lamps can be used. Also, the direct type backlight unit is easy to handle and can be used for LCD devices having a large screen over 20 inches because there is no limit in the size of a display area.
Meanwhile, the LCD device having such backlight units is a hold type illumination so that complete moving picture display may be difficult. That is, when a moving picture is displayed with the LCD device, so-called motion blurring in the display of a moving picture, that is, moving picture contour degradation, may be generated due to the hold characteristic so that the image quality is deteriorated. Thus, to prevent the moving picture motion blurring in the display of a moving picture, that is, moving picture contour degradation, the LCD device of a backlight scanning system (a sequential driving system) using a direct type backlight unit in which a plurality of lamps are horizontally arranged has been suggested.
According to the LCD device of the scanning backlight driving system, the lamps are lit in synchronism with a start time of a scanning signal of a display image and simultaneously, when a brightness signal of the same level is supplied, the display brightness of the liquid crystal panel is set such that a time-integrated factor of a brightness value between frames can be equal. Thus, the LCD device of the scanning backlight driving system may achieve impulse type light emission (illumination) equivalent to a cathode ray tube (CRT) so that the moving picture contour degradation in the display of a moving picture may be prevented.
The scanning backlight driving system is a technique to turn off an unnecessary screen by instantly turning off the lamps when an image is displayed on the liquid crystal panel, which requires individual driving of the lamps. To individually drive the lamps, the lamps are electrically connected to an external inverter via a wire work so that a driving voltage generated by the inverter may be supplied to the lamps.
Although the scanning backlight driving system that individually turns the lamps on/off may prevent motion blurring (moving picture contour degradation), as the number of lamps that are individually driven increases, the burden of the wire work and a connection process of coupling a wire and the inverter increases, thus raising the manufacturing costs.